Typically error-prone 49ers lead NFL in key category

There are various reasons, which include the defense (No. 7 in the NFL), the special teams (Andy Lee, David Akers, Ted Ginn) and the schedule (Seahawks, Bengals).

But there’s another factor that’s flown mostly under the radar: The 49ers are tied for the NFL lead in turnover differential (+6) with the Lions (3-0) and the Ravens (2-1).

How unusual is that? From 2004-10, the Niners forced more turnovers than they lost just once (2009) and had a turnover differential of -54 during that seven-year span.

A big reason for the early season shift has been Alex Smith, who has thrown one interception in 74 attempts, continuing a trend that began last year. Since Oct. 17, 2010, Smith has thrown two interceptions in 224 attempts and has the NFL’s lowest interception percentage (0.9) over that time span.

Sunday’s game against the Eagles, of course, could force the Niners’ risk-averse offense out of its dink-and-dunk comfort zone. San Francisco, which is an 8 1/2-point underdog, has never trailed by more than three points this season, allowing them to play conservatively.

Smith has avoided mistakes in his role as game manager.

On Sunday, he might be forced to take the next step and avoid errors while the Niners attempt to keep pace with Philadelphia.